The SSH model describes noninteracting quantum particles hopping in a 1D lattice
with alternating hopping coefficients.
Varying the hopping ratio, the topological trivial phase or nontrivial phase appears,
depending on the hopping term on the end of SSH model is strong or weak [1]}.
For a noninteracting topological insulator, edge
degeneracy comes directly from the zero-energy edge mode,
which is protected by its topological invariants of the bulk crystal through the
bulk-edge correspondence.
After considering the interaction, the SSH model exhibits a rich phase diagram [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, where the single-particle picture is not applicable.
